Abstract:
The presentation is divided in two parts. In the first part, an algorithm to remove the multipath effect in SAR images is presented. Currently, the radome containing the F-SAR antenna is located at the bottom of the plane, which in combination with strong side lobes in the antenna pattern results in a multipath component in the SAR signal. The undesired effects are mainly range undulations in the amplitude and the phase of the processed image. An algorithm to remove the multipath is presented and validated with along-track interferometric and polarimetric data.
The second part of the work presents results with circular SAR. With a circular SAR acquisition it is possible to obtain information of the scene with 360° aspect angle observation, resulting in images with sub-wavelength resolution, as well as the possibility to perform 3-D image reconstruction (tomography). Algorithms to perform radiometric calibration and autofocus are presented, as well as 2-D and 3-D processing results with data acquired by both E-SAR (L-band) and F-SAR (X-band) systems.

Abstract:
The capability of microwaves to penetrate trough foliage (FOLPEN), combined with the potentialities of POLinSAR are demonstrated to be valid instruments for the investigation of forest biophysical and structural characteristics and detection of camouflaged targets. However, the complexity of the interactions of different forest elements can lead to unexpected results. In this context, a polarimetric and interferometric backscattering simulator (PRIS) is a valid instrument for studing the forest electromagnetic return.

Abstract:
In the frame of the ARGOS project a near-real time onboard processor for Ground Moving Target Identification (GMTI) should be developed for the F-SAR system. The objective of the work is to develop a fast moving target position and motion parameter estimation procedure. Since after common SAR focusing the moving targets become displaced in azimuth and range, by measuring the offset it is possible to estimate their motion parameters as well as their true beam center positions. The offset measurement requires, however, A Priori knowledge, i.e. the exact road position within the SAR image. The innovation of the presented work is mainly the pre-processing step: SAR focusing and dual-channel calibration is quickened by selecting only relevant parts of the range compressed data – namely a few patches that cover all the roads of interest in the dataset. Besides no further adaptive focusing for each target is necessary, as the algorithm relies just in the detected target position at the commonly focused SAR data. In addition, the target velocity estimation (both across- and along-track components) makes use not only of the azimuth displacement to the road, but also of the often disregarded range shift. Furthermore, as the commonly focused signal is still too smeared for an accurate displacement measurement, a refinement in the Doppler domain is employed to get a sharper detection and hence a more accurate motion parameter estimation. The algorithm description comprehends mainly the coordinate transformation - latitude/longitude to range/azimuth – and an iterative procedure for accurate displacement and velocity estimation. The implemented program output is both the target motion parameters and the “true” geographic coordinates. The whole procedure has been verified with real F-SAR data.

Abstract:
Moving targets can be detected by a Synthetic Aperture Radar with two or more phase centres, which are displaced in along-track direction. The most common moving target indication (MTI) techniques are Along-Track-Interferometry (ATI) and Displaced Phase Centre Antenna (DPCA). Moving target detection is complicated by the fact that moving target signals interfere with stationary target signals, so called clutter. With only one detection threshold for the whole scene, the false alarm rate varies as the clutter changes. To achieve constant false alarm rate (CFAR) detection, the detection threshold has to be locally adapted.
In this work statistical analysis of ATI and DPCA signals and the estimation of clutter statistics are presented. Determination of constant false alarm threshold is described and theoretical analyses are verified with real airborne experimental data from F-SAR.

Markus Bachmann "TerraSAR-X Antenna Characterisation"

Abstract:
DLR's TerraSAR-X was launched successfully in June 2007. An important aspect of the satellite is the Antenna Model. It describes the radiation characteristics of the SAR Antenna, which are needed for pattern correction of the SAR images. Much effort was spent to establish and verify the Antenna Model very accurately to minimize costs and time needed for the calibration activities.
The presentation will give an overview on the general approach of the Antenna Model. The design and integration within the ground segment as well as the applications of the antenna model in context with TerraSAR-X will be shown. Finally, the on-ground validation performed before launch and especially the results of antenna pattern verification during the calibration campaign in the second half of 2007 are discussed in detail.

Abstract:
The work, sponsored by SELEX-GEMATRONIK, focuses on the implementation of aperture synthesis for ground-based coherent radars. Such systems can take advantage of the circular trajectory of the antenna phase centre to synthesize an antenna aperture useful for resolution improvement. The performance of azimuth compression algorithms is analysed in detail for the case of radar meteorological targets (precipitation and clutter).
Advanced array signal processing techniques for obtaining super-resolution imaging of coherent targets are also investigated. A quite unique experimental setup allowed the comparison between two ground-based SAR systems with regards to resolution of coherent (clutter) and partially coherent (precipitation) targets. Doppler velocity and spectral width estimation, as well as accuracy of reflectivity measurements are also addressed.
All data were kindly provided by SELEX-GEMATRONIK.

Abstract:
The problem of hard target detection under forest canopy using imaging radars is examined. Current methods for this problem are heuristic and are based on the application low frequency radar systems operating at lower VHF band of the spectrum. Such techniques suffer from poor image resolution, poor backscatter to radio signal interferer ratio, and high false alarm rates. To examine this problem thoroughly, comprehensive high fidelity foliage and hard target models based on hybrid single scattering theory for foliage and FDTD as well as iterative PO model for hard targets are developed. Polarimetry is used for demonstrating achievable enhancement in signal to clutter ratio if polarimetric radars were to be used. Also the concept of a 3-D beam-scanning SAR system operating at millimeter-wave frequencies is presented for foliage camouflaged hard target detection and identification. Experimental results are demonstrated for the proof of concept.

Ali Eren Culhaoglu "Metamaterials - A New Class of Materials in Electrical Engineering"

Abstract:
Metamaterials are a new class of artificially structured materials, which exhibit unusual properties not observed in nature. The most prominent example of these are metamaterials with a negative index of refraction, a fundamental consequence of which is the reversal of Snell's Law. This phenomenon was theoretically predicted in 1968 and demonstrated in microwave scattering experiments in 2000. Over the last several years there has been a surge of interest in metamaterials because of their potential to expand the range of available electromagnetic properties of materials. The presentation will review this new emerging field and its potential applications. In particular, application of metamaterials to reduction of radar visibility of targets (electromagnetic cloaking) will be discussed.
The presentation will address the following topics:
- Characteristics and Physical Properties of Metamaterials
- Types of Metamaterials
- Potential Applications of Metamaterials